When a sewage treatment plant dumps warm water into a nearby river, it’s a problem for cold-blooded fish. On the Rogue River in Oregon–known for its salmon and steelhead–the wastewater plant in Medford, Oregon, considered building an expensive cooling tower to solve the problem. It ended up using trees instead.

The plant started working with farmers and other landowners along the river, paying them to plant trees by the water–which proved an equally effective cooling mechanism as traditional infrastructure. The key was location: the Freshwater Trust, a nonprofit that worked on the project, created a data analysis tool to identify a dozen properties, out of hundreds, where trees could have the most impact.